JP2010183242A - Communication device and dns proxy server - Google Patents

Abstract

A technique capable of reducing the load on a DNS proxy server is provided.
In a network having an IPv4 DNS server 40 that performs name resolution in an IPv4 address space, an IPv6 DNS server 50 that performs name resolution in an IPv6 address space, and a DNS proxy server 30 that requests name resolution from the IPv6 DNS server 50, The IPv4 terminal 10 that communicates, when requested to resolve the name of another communication device, a first name resolution request means for requesting the IPv4 DNS server 40 to resolve the name of the other communication device, and a first name resolution request And a second name resolution requesting means for requesting the DNS proxy server 30 for name resolution of the other communication apparatus when the IPv4 address of the other communication apparatus is not obtained by the means.
[Selection] Figure 2

Description

  The present invention relates to a communication device and a DNS proxy server.

  FIG. 5A shows a network configuration when a terminal that supports only IPv4 (IPv4 terminal) connects to a server that supports only IPv6 (IPv6 server). Communication between the IPv4 terminal and the IPv6 server is performed via a translator that converts the IPv4 packet and the IPv6 packet. Also, the DNS proxy server temporarily assigns an IPv4 address to the IPv6 address of the IPv6 server, and notifies the IPv4 terminal of the address. A packet from the IPv4 terminal to the IPv6 server is transmitted to the IPv4 address notified from the DNS proxy server. In the translator, the destination of the packet is converted into the IPv6 address of the IPv6 server and transmitted to the IPv6 server. The communication between the IPv6 terminal and the IPv4 server is the same operation.

  FIG. 5B is a sequence diagram when the IPv4 terminal inquires about the IP address of the IPv6 server. First, the IPv4 terminal queries the DNS proxy server for the IPv4 address of the IPv6 server (qtype = A). The DNS proxy server inquires another DNS server about the IPv4 address of the IPv6 server to be inquired. In response to the inquiry, when a response indicating that the address does not exist is received (in the DNS response, a message with an Rcode value = 0 and an empty response part is received), an IPv6 address is inquired. When a response of the IPv6 address is received, an IPv4 address is temporarily assigned to the IPv6 address, and the assigned IPv4 address is notified to the IPv4 terminal.

JP 2003-198639 A

  However, the above configuration has a problem that the load on the DNS proxy server increases. Normally, when the communication partner of the IPv4 terminal supports IPv4, the IPv4 terminal does not need to make an address inquiry to the DNS proxy server, but when the communication partner supports only IPv6, the IPv6 of the communication partner In order to assign an IPv4 address corresponding to the address, it is necessary to make an address inquiry to the DNS proxy server. However, since an ordinary IPv4 terminal does not have a means of knowing whether the communication partner is compatible with IPv4 or only IPv6 before the address inquiry, the address inquiry is always made to the DNS proxy server. Also, since the DNS proxy server that has received an address inquiry from an IPv4 terminal does not have a means for knowing in advance whether the inquiry partner has an IPv4 address or only an IPv6 address, it first inquires about the IPv4 address of the other party. If the other party does not have an IPv4 address, the IPv6 address is inquired. For this reason, the DNS proxy server has a property that the number of inquiry processing is larger than that of a normal DNS server.

  This invention is made | formed in view of the subject mentioned above, Comprising: It aims at providing the technique which can reduce the load of a DNS proxy server.

  In order to solve the above problem, a communication apparatus according to an aspect of the present invention includes an IPv4 DNS server that performs name resolution in an IPv4 address space, an IPv6 DNS server that performs name resolution in an IPv6 address space, and a DNS that requests name resolution from an IPv6 DNS server. A communication device that communicates with another communication device in a network having a proxy server, and requests a name resolution of the other communication device from the IPv4 DNS server when the name resolution of the other communication device is requested A resolution requesting means; and a second name resolution requesting means for requesting the DNS proxy server for name resolution of another communication apparatus when the IPv4 address of the other communication apparatus cannot be obtained by the first name resolution requesting means. It is characterized by providing.

  In the communication apparatus, the second name resolution requesting unit may further notify the DNS proxy server that there is no IPv4 address of another communication apparatus.

In order to solve the above problem, a communication apparatus according to another aspect of the present invention requests name resolution from an IPv4 DNS server that performs name resolution in an IPv4 address space, an IPv6 DNS server that performs name resolution in an IPv6 address space, and an IPv4 DNS server. A communication device that communicates with another communication device in a network having a DNS proxy server, and requests a name resolution of the other communication device from the IPv6 DNS server when the name resolution of the other communication device is requested. Name resolution requesting means and second name resolution requesting means for requesting the DNS proxy server for name resolution of another communication apparatus when the IPv6 address of the other communication apparatus cannot be obtained by the first name resolution requesting means. It is characterized by providing.

  In the communication apparatus, the second name resolution requesting unit may further notify the DNS proxy server that there is no IPv6 address of another communication apparatus.

  In order to solve the above problem, a DNS proxy server according to another aspect of the present invention includes a DNS proxy that requests name resolution from an IPv4 DNS server that performs name resolution in an IPv4 address space and an IPv6 DNS server that performs name resolution in an IPv6 address space. When it is notified from the one communication device that the IPv4 address of the other communication device does not exist, the server requests the IPv6 DNS server to resolve the name of the other communication device, while the other communication device requests other communication. When it is notified that the IPv6 address of the device does not exist, it requests the IPv4 DNS server to resolve the name of another communication device.

  The DNS proxy server includes a request accepting unit that accepts a name resolution request of another communication device from one communication device, and information indicating that the IPv4 address of the other communication device does not exist in the name resolution request accepted by the request accepting unit Alternatively, a request confirmation unit that determines whether or not information indicating that the IPv6 address of the other communication device does not exist is included, and that the IPv4 address of the other communication device does not exist in the name resolution request by the request confirmation unit. First name resolution requesting means for requesting the IPv6 DNS server to resolve the name of another communication apparatus when it is determined that the information to be included is included, and the IPv6 address of the other communication apparatus in the name resolution request by the request confirmation means IPv4 DNS server that resolves the name of another communication device when it is determined that information indicating that does not exist is included It may be provided with a second name resolution request means for requesting.

  According to the present invention, since the number of address queries from the communication terminal to the DNS proxy server and the number of address queries from the DNS proxy server to the DNS server are reduced, the load on the DNS proxy server is reduced.

It is a schematic diagram of the network 1 provided with the DNS proxy server 30 which is an example of this invention. It is a block diagram of the IPv4 communication terminal 10, the IPv6 communication terminal 20, and the DNS proxy server 30 which are examples of this invention. Operations of the IPv4 terminal 10 and the IPv6 terminal 20 will be described. FIG. 3 is a sequence diagram of an IPv4 terminal 10, a DNS proxy server 30, an IPv4 DNS server 40, and an IPv6 DNS server 50. It is a figure for demonstrating the prior art.

  Embodiments of the present invention will be described below with reference to the drawings. The network 1 is, for example, the Internet, and includes an IPv4 DNS server 40 that performs name resolution in the IPv4 address space and an IPv6 DNS server 50 that performs name resolution in the IPv6 address space, as shown in FIG. The network 1 includes a DNS proxy server 30 (corresponding to the DNS proxy server of the present invention) in addition to the IPv4 DNS server 40 and the IPv6 DNS server 50. Further, an IPv4 terminal 10 (corresponding to the communication apparatus of the present invention) and an IPv6 terminal 20 (corresponding to the communication apparatus of the present invention) are connected to the network 1.

  As shown in FIG. 2A, the IPv4 terminal 10 includes a storage unit 100, an application processing unit 110, a resolver (resolver) 120, and a DNS proxy unit 130 (first name resolution requesting means and second name of the present invention). In charge of solution request means). The storage unit 100 stores various information. For example, the storage unit 100 stores information referred to by the application processing unit 110, information generated by the application processing unit 110, IP addresses of the IPv4 DNS server 40 and the DNS proxy server 30, and the like. Note that the IP addresses of the IPv4 DNS server 40 and the DNS proxy server 30 stored in the storage unit 100 are acquired by DHCP, for example.

  The application processing unit 110 executes various processes. An example of the application processing unit 110 is a browser that browses Web pages. When communicating with another communication device, the application processing unit 110 requests the resolver 120 to resolve the name of the other communication device when the IP address of the other communication device is unknown. In other words, the application processing unit 110 makes an address inquiry of the communication partner by calling the resolver 120.

  The resolver 120 receives a request for name resolution of another communication device from the application processing unit 110. When the resolver 120 receives a request for name resolution of another communication device from the application processing unit 110, the resolver 120 requests the DNS proxy unit 130 for name resolution in the IPv4 address space of the other communication device.

  The DNS proxy unit 130 receives a request for name resolution of another communication device from the resolver 120. When the DNS proxy unit 130 receives a request for name resolution of another communication device from the resolver 120, the DNS proxy unit 130 refers to the IP address of the IPv4 DNS server 40 stored in the storage unit 100 and performs name resolution of the other communication device. Information related to the request (hereinafter referred to as a DNS message, referred to as “name resolution request information”) is transmitted to the IPv4 DNS server 40 (first name resolution request means).

  The DNS proxy unit 130 receives information related to a response to the name resolution request information (hereinafter referred to as “name resolution response information”) from the IPv4 DNS server 40. When the name resolution response information received from the IPv4 DNS server 40 includes the IPv4 address of another communication device that has requested name resolution, that is, the DNS proxy unit 130 requests other name communication from the IPv4 DNS server 40. When the IPv4 address of the device is acquired, the IPv4 address of the other communication device is supplied to the resolver 120.

  When the name resolution response information received from the IPv4 DNS server 40 does not include the IPv4 address of another communication device that has requested name resolution, that is, the DNS proxy unit 130 has received another name resolution request from the IPv4 DNS server 40. When the IPv4 address of the communication device cannot be acquired, the name resolution request information related to the other communication device is transmitted to the DNS proxy server 30 (second name resolution request means). When the DNS proxy unit 130 cannot acquire the IPv4 address of the other communication device from the IPv4 DNS server 40, the DNS proxy unit 130 notifies the DNS proxy server 30 that the IPv4 address of the other communication device does not exist (second). Name resolution request means). For example, the DNS proxy unit 130 transmits name resolution request information including information indicating that the IPv4 address of the other communication device does not exist to the DNS proxy server 30 (second name resolution request unit).

  The DNS proxy unit 130 receives name resolution response information from the DNS proxy server 30. When the name resolution response information received from the DNS proxy server 30 includes the IPv4 address of another communication device that has requested the name resolution, the DNS proxy unit 130 requests the name resolution from the DNS proxy server 30. When the IPv4 address of the other communication device is acquired, the IPv4 address of the other communication device is supplied to the resolver 120.

  As shown in FIG. 2B, the IPv6 terminal 20 includes a storage unit 200, an application processing unit 210, a resolver (resolver) 220, and a DNS proxy unit 230 (first name resolution requesting means and second name of the present invention). In charge of solution request means). The storage unit 200 stores various information. For example, the storage unit 200 stores information referred to by the application processing unit 210, information generated by the application processing unit 210, IP addresses of the IPv6 DNS server 50 and the DNS proxy server 30, and the like.

  The application processing unit 210 executes various processes. An example of the application processing unit 210 is a browser that browses Web pages. When communicating with another communication device, the application processing unit 210 requests the resolver 220 to resolve the name of the other communication device when the IP address of the other communication device is unknown.

  The resolver 220 receives a request for name resolution of another communication device from the application processing unit 210. When the resolver 220 receives a request for name resolution of another communication device from the application processing unit 210, the resolver 220 requests the DNS proxy unit 230 for name resolution in the IPv6 address space of the other communication device.

  The DNS proxy unit 230 receives a request for name resolution of another communication device from the resolver 220. When the DNS proxy unit 230 receives a request for name resolution of another communication device from the resolver 220, the DNS proxy unit 230 refers to the IP address of the IPv6 DNS server 50 stored in the storage unit 200 to resolve the name of the other communication device. Such name resolution request information is transmitted to the IPv6 DNS server 50 (first name resolution request means).

  The DNS proxy unit 130 receives name resolution response information from the IPv6 DNS server 50. If the IPv6 address of another communication device that has requested name resolution is included in the name resolution response information received from the IPv6 DNS server 50, that is, the other communication that has requested name resolution from the IPv6 DNS server 50. When the IPv6 address of the device is acquired, the IPv6 address of the other communication device is supplied to the resolver 220.

  The DNS proxy unit 230 does not include the IPv6 address of the other communication device that has requested name resolution in the name resolution response information received from the IPv6 DNS server 50, that is, other names that have requested name resolution from the IPv6 DNS server 50. When the IPv6 address of the communication device cannot be acquired, the name resolution request information related to the other communication device is transmitted to the DNS proxy server 30 (second name resolution request means). Further, when the DNS proxy unit 230 cannot acquire the IPv6 address of the other communication device from the IPv46 NS server 40, the DNS proxy unit 230 notifies the DNS proxy server 30 that the IPv6 address of the other communication device does not exist (second). Name resolution request means). For example, the DNS proxy unit 230 transmits name resolution request information including information indicating that the IPv6 address of the other communication device does not exist to the DNS proxy server 30 (second name resolution request unit).

  The DNS proxy unit 230 receives name resolution response information from the DNS proxy server 30. The DNS proxy unit 230, when the name resolution response information received from the DNS proxy server 30 includes the IPv6 address of another communication device that has requested name resolution, that is, the DNS proxy server 30 has requested name resolution. When the IPv6 address of the other communication device is acquired, the IPv6 address of the other communication device is supplied to the resolver 220.

  As shown in FIG. 2C, the DNS proxy server 30 includes a storage unit 300 and a DNS proxy unit 330 (request receiving unit, request confirmation unit, first name resolution request unit, and second name resolution request of the present invention. In charge of means). The storage unit 300 stores various information. For example, the storage unit 300 stores the IP addresses of the IPv4 DNS server 40 and the IPv6 DNS server 50, and the like.

  The DNS proxy unit 330 receives a name resolution request from another communication device from one communication device (request reception means). That is, the DNS proxy unit 330 receives name resolution request information of another communication device from one communication device. For example, the DNS proxy unit 330 receives name resolution request information of the IPv6 terminal 20 from the IPv4 terminal 10. For example, the DNS proxy unit 330 receives the name resolution request information of the IPv4 terminal 10 from the IPv6 terminal 20.

  The DNS proxy unit 330 determines whether the received name resolution request information includes information indicating that the IPv4 address of the other communication device does not exist or information indicating that the IPv6 address of the other communication device does not exist. (Request confirmation means).

  When the DNS proxy unit 330 determines that the name resolution request information includes information indicating that the IPv4 address of the other communication device does not exist, the DNS proxy unit 330 sends the name resolution request information related to the other communication device to the IPv6 DNS server. Request (first name resolution request means). For example, if the DNS proxy unit 330 determines that the name resolution request information received from the IPv4 terminal 10 includes information indicating that the IPv4 address of the IPv6 terminal 20 does not exist, the name resolution related to the IPv6 terminal 20 Requests the request information from the IPv6 DNS server 50.

  The DNS proxy unit 330 receives name resolution response information from the IPv6 DNS server 50. That is, the DNS proxy unit 330 acquires the IPv6 address of another communication device (for example, the IPv6 terminal 20) from the IPv6 DNS server 50. The DNS proxy unit 330 that has acquired the IPv6 address of another communication device (for example, the IPv6 terminal 20) from the IPv6 DNS server 50 assigns one unique IPv4 address to the IPv6 address (converts the address space), and The IPv4 address is transmitted to the one communication device (for example, IPv4 terminal 10) that is the request source.

  When the DNS proxy unit 330 determines that the name resolution request information includes information indicating that the IPv6 address of the other communication device does not exist, the DNS proxy unit 330 sends the name resolution request information related to the other communication device to the IPv4 DNS server. Request (second name resolution request means). For example, if the DNS proxy unit 330 determines that the name resolution request information received from the IPv6 terminal 20 includes information indicating that the IPv6 address of the IPv4 terminal 10 does not exist, the name resolution related to the IPv4 terminal 10 Requests the request information from the IPv4 DNS server 40.

  The DNS proxy unit 330 receives name resolution response information from the IPv4 DNS server 40. That is, the DNS proxy unit 330 acquires the IPv4 address of another communication device (for example, the IPv4 terminal 10) from the IPv4 DNS server 40. The DNS proxy unit 330 that has acquired the IPv4 address of another communication device (for example, the IPv4 terminal 10) from the IPv4 DNS server 40 assigns one unique IPv6 address to the IPv4 address (converts the address space), and The IPv6 address is transmitted to the one communication device (for example, IPv6 terminal 20) that is the request source.

  Next, operations of the IPv4 terminal 10 and the IPv6 terminal 20 will be described. 3A is a flowchart showing the operation of the IPv4 terminal 10, and FIG. 3B is a flowchart showing the operation of the IPv6 terminal 20. The flowchart shown in FIG. 3A starts when the DNS proxy unit 130 receives a request (inquiry) for name resolution of a certain terminal (target host) from the resolver 120. The flowchart shown in FIG. The process starts when the proxy unit 230 receives a request for name resolution of a certain terminal (target host) from the resolver 220.

  3A, the DNS proxy unit 130 that has received a request for name resolution of the target host from the resolver 120 inquires the IPv4 DNS server 40 about the IP address (IPv4 address) of the target host (step S100). Specifically, the DNS proxy unit 130 transmits a DNS message whose qtype is A (IPv4 address) to the IPv4 DNS server 40. Subsequently, the DNS proxy unit 130 determines whether or not the IP address (IPv4 address) of the target host has been acquired from the IPv4 DNS server 40 (step S110).

  When the DNS proxy unit 130 determines that the IP address (IPv4 address) of the target host has been acquired from the IPv4 DNS server 40 (step S110: Yes), the DNS proxy unit 130 supplies the IP address (IPv4 address) to the resolver 120 (step S120). . And this flowchart is complete | finished.

  On the other hand, when the DNS proxy unit 130 determines that the IP address (IPv4 address) of the target host has not been acquired from the IPv4 DNS server 40 (step S110: No), the DNS proxy server 30 sends the IP address (IPv4 address of the target host). ) (Step S130). Specifically, the DNS proxy unit 130 transmits a DNS message including information indicating that qtype is A (IPv4 address) and the IPv4 address of the target host does not exist to the DNS proxy server 30. As a technique for adding the information indicating that the information does not exist to the DNS message, a technique using the Opcode field (4 bits) of the DNS message is conceivable. According to the website (http://www.iana.org/assignments/dns-parameters), the value of the Opcode field is assigned (reserved) from 0 to 5 according to the website (http://www.iana.org/assignments/dns-parameters). No. 15 are not assigned.

  Following step S130, the DNS proxy unit 130 supplies the resolver 120 with the IP address (IPv4 address) acquired from the DNS proxy server 30 (step S140). And this flowchart is complete | finished. Note that the DNS proxy server 30 that has received the DNS message including the information indicating that the IPv4 address of the target host does not exist from the DNS proxy unit 130 inquires of the IPv6 DNS server 50 about the IPv6 address of the target host. The IPv4 address is temporarily assigned to the IPv6 address thus assigned, and the assigned IPv4 address is returned to the DNS proxy unit 130.

  In FIG. 3B, the DNS proxy unit 230 that has received the request for name resolution of the target host from the resolver 220 inquires the IPv6 DNS server 50 about the IP address (IPv6 address) of the target host (step S200). Specifically, the DNS proxy unit 230 transmits a DNS message whose qtype is AAAA (IPv6 address) to the IPv6 DNS server 50. Subsequently, the DNS proxy unit 230 determines whether or not the IP address (IPv6 address) of the target host has been acquired from the IPv6 DNS server 50 (step S210).

  When the DNS proxy unit 230 determines that the IP address (IPv6 address) of the target host has been acquired from the IPv6 DNS server 50 (step S210: Yes), the DNS proxy unit 230 supplies the IP address (IPv6 address) to the resolver 220 (step S220). . And this flowchart is complete | finished.

  On the other hand, when the DNS proxy unit 230 determines that the IP address (IPv6 address) of the target host has not been acquired from the IPv6 DNS server 50 (step S210: No), the DNS proxy server 30 sends the IP address (IPv6 address) of the target host. ) (Step S230). Specifically, the DNS proxy unit 230 transmits a DNS message including information indicating that qtype is AAAA (IPv6 address) and the IPv6 address of the target host does not exist to the DNS proxy server 30. The method of adding the information indicating that the information does not exist to the DNS message is the same as that of the IPv4 terminal 10 shown in FIG.

  Subsequent to step S230, the DNS proxy unit 230 supplies the resolver 220 with the IP address (IPv6 address) acquired from the DNS proxy server 30 (step S240). And this flowchart is complete | finished. The DNS proxy server 30 that has received the DNS message including the information that the IPv6 address of the target host does not exist from the DNS proxy unit 230 inquires of the IPv4 DNS server 40 for the IPv4 address of the target host. The IPv6 address is temporarily assigned to the assigned IPv4 address, and the assigned IPv6 address is returned to the DNS proxy unit 230.

  Next, operations of the IPv4 terminal 10 (the resolver 120 and the DNS proxy unit 130), the DNS proxy server 30, the IPv4 DNS server 40, and the IPv6 DNS server 50 will be described. In the case of the IPv6 terminal 20, the sequence is the same except that the IPv4 address and the IPv6 address are interchanged. The sequence diagram shown in FIG. 4 is a sequence when the IPv4 terminal 10 inquires about the IP address of the IPv6 terminal 20, and the DNS proxy unit 130 in the IPv4 terminal 10 makes an inquiry about the IP address of the IPv6 terminal 20 from the resolver 120. It starts by accepting (Seq1). The DNS proxy unit 130 transmits a DNS message whose qtype is A (IPv4 address) to the IPv4 DNS server 40 (Seq2). The IPv4 DNS server 40 responds to the DNS proxy unit 130 that the IPv4 address of the IPv6 terminal 20 does not exist (that the IPv4 address of the IPv6 terminal 20 could not be acquired) (Seq3). The DNS proxy unit 130 transmits a DNS message including information indicating that qtype is A (IPv4 address) and the IPv4 address of the IPv6 terminal 20 does not exist to the DNS proxy server 30 (Seq4). The DNS proxy server 30 transmits a DNS message whose qtype is AAAA (IPv6 address) to the IPv6 DNS server 50 (Seq5). The IPv6 DNS server 50 responds to the DNS proxy server 30 with the IPv6 address of the IPv6 terminal 20 (Seq6). The DNS proxy server 30 responds to the DNS proxy unit 130 with the IPv4 address mapped to the IPv6 address acquired in Seq6 (Seq7). The DNS proxy unit 130 responds to the resolver 120 with the mapped IPv4 address (Seq8).

  As described above, according to the embodiment of the present invention, the number of address inquiries from the IPv4 terminal 10 and the IPv6 terminal 20 to the DNS proxy server 30 and the addresses from the DNS proxy server 30 to the IPv4 DNS server 40 and the IPv6 DNS server 50 are as follows. Since the number of inquiries is reduced, the load on the DNS proxy server is reduced. Accordingly, it is possible to reduce a large load on the DNS proxy server in a large-scale network in which a network in the IPv4 address space and a network in the IPv6 address space are interconnected.

  In FIG. 1, the IPv4 terminal 10 and the IPv6 terminal 20 are personal computers, but the communication apparatus of the present invention is not limited to this and may be any apparatus that can be connected to the network 1. For example, it may be a mobile phone (mobile station), a game machine, a music playback device, or the like. Further, in the present embodiment, the DNS proxy unit 130 of the IPv4 terminal 10 implements the first and second name resolution requesting means based on the request from the resolver 120 of the IPv4 terminal 10, but the DNS proxy of the IPv4 terminal 10 The unit 130 may implement the first and second name resolution requesting means based on a request from another device (arbitrary IPv4 terminal). That is, the communication apparatus of the present invention may be a server (for example, a forward proxy server connected to an IPv4 terminal). Similarly, the DNS proxy unit 230 of the IPv6 terminal 20 implements the first and second name resolution requesting means based on the request from the resolver 220 of the IPv6 terminal 20, but the DNS proxy unit 230 of the IPv6 terminal 20 The first and second name resolution requesting means may be implemented based on a request from another device (any IPv6 terminal). That is, the communication apparatus of the present invention may be a server (for example, a forward proxy server connected to an IPv6 terminal).

  In addition, the program for performing each process of each apparatus of the IPv4 terminal 10, the IPv6 terminal 20, and the DNS proxy server 30 by one Embodiment of this invention is recorded on a computer-readable recording medium, and is recorded on the said recording medium The above-described various processes related to the communication apparatus and the DNS proxy server according to the embodiment of the present invention may be performed by causing the computer system to read and execute the program. Here, the “computer system” may include an OS and hardware such as peripheral devices. Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used. The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

  Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic DRAM) in a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  1 Network 10 IPv4 Terminal 20 IPv6 Terminal 30 DNS Proxy Server 40 IPv4 DNS Server 50 IPv6 DNS Server 100 Storage Unit 110 Application Processing Unit 120 Resolver 130 DNS Proxy Unit 200 Storage Unit 210 Application Processing Unit 220 Resolver 230 DNS Proxy Unit 300 D Storage Unit 330 Part

Claims (6)

A communication device that communicates with other communication devices in a network having an IPv4 DNS server that performs name resolution in an IPv4 address space, an IPv6 DNS server that performs name resolution in an IPv6 address space, and a DNS proxy server that requests name resolution from an IPv6 DNS server,
First name resolution requesting means for requesting the IPv4 DNS server to resolve the name of the other communication device when the name resolution of the other communication device is requested;
Second name resolution requesting means for requesting the DNS proxy server to perform name resolution of the other communication device when the IPv4 address of the other communication device cannot be obtained by the first name resolution requesting unit. A communication device. The second name resolution request means further includes:
The communication apparatus according to claim 1, wherein a DNS proxy server is notified that the IPv4 address of the other communication apparatus does not exist. A communication device that communicates with other communication devices in a network having an IPv4 DNS server that performs name resolution in an IPv4 address space, an IPv6 DNS server that performs name resolution in an IPv6 address space, and a DNS proxy server that requests name resolution from an IPv4 DNS server,
First name resolution requesting means for requesting an IPv6 DNS server for name resolution of the other communication device when name resolution of the other communication device is requested;
And a second name resolution requesting means for requesting a DNS proxy server for name resolution of the other communication device when the IPv6 address of the other communication device cannot be obtained by the first name resolution requesting means. A communication device. The second name resolution request means further includes:
The communication apparatus according to claim 3, wherein a DNS proxy server is notified that an IPv6 address of the other communication apparatus does not exist.   An IPv4 DNS server that performs name resolution in an IPv4 address space and a DNS proxy server that requests name resolution from an IPv6 DNS server that performs name resolution in an IPv6 address space, and that there is no IPv4 address of another communication device from one communication device Is notified to the IPv6 DNS server while the other communication device is notified that the IPv6 address of the other communication device does not exist. A DNS proxy server that requests name resolution from an IPv4 DNS server. The DNS proxy server
Request accepting means for accepting a name resolution request of another communication device from one communication device;
Whether the name resolution request received by the request receiving means includes information indicating that the IPv4 address of the other communication device does not exist or information indicating that the IPv6 address of the other communication device does not exist A request confirmation means for determining
When it is determined by the request confirmation means that the name resolution request includes information indicating that the IPv4 address of the other communication device does not exist, the name resolution request of the other communication device is requested to the IPv6 DNS server. First name resolution request means;
When it is determined by the request confirmation means that the name resolution request includes information indicating that the IPv6 address of the other communication device does not exist, a request for name resolution of the other communication device is made to the IPv4 DNS server. 6. The DNS proxy server according to claim 5, further comprising second name resolution requesting means.

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